Various antenna switches and adapters are known, and one, particularly, describes an antenna switch which permits a car antenna to, selectively, operate a car radio receiver or a 27 MHz citizen band radio. The antenna switch there shown has the disadvantage that it is entirely passive and thus is not capable of handling transmission power of a high-frequency transceiver, such as a portable telephone. Such portable telephones have very low transmission power, and a passive network, as known, has an excessive insertion loss so that the transmission power available for radiation from the known switch is not suitable for use with portable or radio telephones.